Print hammer for high-speed printer

ABSTRACT

An electromagnetically actuated print hammer comprises two rockers independently pivoted on a common axle, one rocker carrying a striker and being urged by spring force against the other rocker which has a long lever arm acting upon the strikercarrying rocker and a short lever arm carrying an armature attractable by an electromagnet; upon energization of the electromagnet, the armature-carrying rocker is arrested before the striker contacts the working surface.

United States Patent Pipitone [4 1 Feb. 22, 1972 154] PRINT HAMMER FORHIGH-SPEED PRINTER [72] Inventor: Roberto Pipitone, Milan, Italy [73]Assignee: Societa ltaliana Telecomunicazionl Siemens S.p.A., Milan,Italy [22] Filed: June9, 1969 [21] App1.No.: 831,460

[30] Foreign Application Priority Data June 11, 1968 Italy ..17,577

[52] US. Cl. .....101-/93 C [51] Int. Cl ..B4lg 9/38 [58] Field ofSearch..10l/93 C,93, 297,94; 197/53 [56] References Cited UNITED STATESPATENTS 2,940,385 6/1960 House ..101/93 3,164,085 1/1965 Hawkins..101/93 3,177,803 4/1965 Antonucci 101/93 3,266,418 8/1966 Russo 101/933,349,696 10/1967 Potter.... 101/93 3,385,211 5/1968 Shepard 101/933,442,365 5/1969 Ragland et a1. 197/53 3,504,623 4/1970 Staller ..101/93Primary Examiner-William B. Penn Att0rneyKarl F. Ross [57] ABSTRACT Anelectromagnetically actuated print hammer comprises two rockersindependently pivoted on a common axle, one rocker carrying a strikerand being urged by spring force against the other rocker which has along lever arm acting upon the striker-carrying rocker and a short leverarm carrying an armature attractable by an electromagnet; uponenergization of the electromagnet, the armature-carrying rocker isarrested before the striker contacts the working surface.

11 Claims, 2 Drawing Figures PATENTEUFB22 I972 3.643 594 sum 1 or 2Roberto Pipifone INVENTOR.

WA 6R0 Attorney PRINT HAMMER FOR HIGH-SPEED PRINTER My present inventionrelates to an electromagnetically actuated print hammer of the typeused, for example, in highspeed printers wherein a type carrier, such asa font wheel or ribbon, is continuously rotated so as to present asuccession of type faces to a striker whose actuation at the properinstant causes a corresponding imprint to be made on a paper or otherrecording medium juxtaposed with the type carrier.

In such a system it is essential that the hammer bearing the striker orhead be rapidly advanced and retracted, in order to enable correctselection of the desired character in response to a command pulse and toprevent smearing of the character on the recording medium due toexcessive contact time between this medium and the rotating typecarrier.

The general object of my present invention, therefore, is to provide animproved print hammer which can be rapidly and accurately operated forprinting at high speed.

A more specific object is to provide means in such a device for dampingthe vibrations of the print hammer to allow for a high recurrence rateof the printing strokes.

lt is also an object of my invention to provide a print hammer which,while satisfying the aforestated desiderata, develops sufficient powerto work on a self-contained paper of the ribbonless type which requireda somewhat sharper hammer blow than a paper to be marked by an inkribbon.

The invention also aims at providing a print hammer of compactconstruction and low consumption of electrical energy adapted to realizeall the aforestated objects.

In accordance with this invention, I providean improved print hammerincluding a first rocker carrying an armature and a second rockercarrying a striker, the two rockers being pivotally' mounted on asupport for joint swinging, preferably about a common axis, uponattraction of the armature by energization of a confrontingelectromagnet mounted on the support; the working stroke of thearmature-carrying first rocker is limited by one or more abutments whicharrest that rocker while the second rocker, carrying the hammer head orstriker, continues its swing toward a working surface. Both rockers arerestored to normal by resilient means, such as a coil spring, anchoredto the second rocker so as harmonically to reverse its motion after itskinetic energy has been spent.

Advantageously, in order to improve the operating efficiency of mydevice, the first rocker is of reduced mass compared with thestriker-carrying second rocker which performs the actual printingoperation. To this end, I prefer to make the first rocker of alightweight material, such as aluminum, and to give it the shape of ayoke formed from two generally parallel levers with long and short arms,the free ends of the long arms being interconnected by a bridge piecewhile the short arms are spanned by the armature, e.g., a solid strip ofsoft iron. With both rockers fulcrumed on a common axle parallel to thearmature, the long arms of the first rocker may have their widthsprogressively decreased with increased distances from that axle, i.e.,with increasing moment arm, to save mass and weight. The aforementionedbridge piece may carry a boss directly in line with the striker on theadjoining second rocker and may also coact with an adjustable backstop,such as a micrometric screw, which determines the extent of the returnswing under the urging of the restoring spring and therefore theeffective stroke length of the hammerhead.

The above and other features of my invention will become more fullyapparent from the following detailed description of a preferredembodiment, reference being made to the accompanying drawing in which: 1

FIG. 1 is an exploded perspective view of a print hammer according to myinvention; and

FIG. 2 is a somewhat diagrammatic cross-sectional view of the assemblyof FIG. 1 and associated components of a highspeed printer.

The print hammer shown in the drawing comprises a support 11,illustrated only in part, with a base plate 1 la carrying anelectromagnet generally designated 10. A pair of lugs 13 integral withsupport 11 extend transversely to base plate 11a and have aligned holes14 traversed by an axle 9 which also passes through holes 2a and 3a of apair of rockers 2 and 3. Rocker 3 comprises two generally parallellevers 3b which are fulcrumed on axle 9 and which have long armsinterconnected at their free end by a bridge piece 3c, the latterbearing a boss 6 normally contacting the free end of rocker 2 which isgenerally frame-shaped and is also fulcrumed on axle 9. Levers 3b are ofthe bellcrank type and diminish progressively in width, for the purposestated above, from fulcrum 9 to bridge piece 3c. The short arms of theselevers are spanned by an armature 4 which may consist of soft iron, incontradistinction to the nonmagnetic rocker 3 which is preferably madefrom a light metal such as aluminum or one of its alloys.

A coil spring 8, anchored to an extension 11b of baseplate lla, engagesa tab 2b of rocker 2 so as to urge the latter into contact with boss 6while tending to hold the bridge3c against a seat formed by the tip of amicrometric screw 7 threaded into the base 11. Screw 7 may be adjustedwith the aid of a tool inserted into a slot 7a thereof and may be lockedin position by a counternut 7b.

A striker l on the free end of rocker 2 confronts a working surface hereprovided on a recording medium 15, such as a paper tape, which is drawnby feed rollers 16 past a font wheel 17 carrying a multiplicity of typefaces 17a. An ink ribbon 18 is shown interposed between wheel 17 andrecording tape 15, this ribbon being drawn in the usual manner from areel 18a and wound up on a reel 18b. Operating current, designed todrive the striker 1 toward tape 15 for imprinting thereon a characterrepresented by a confronted type face 17a, is supplied to the coil 10aof electromagnet 10 from a pulse generator 19 which receives commandsignals via a line 20, this pulse generator working into a pair of inputleads 21, 22 which are bridged by a damping circuit, consisting of adiode 23 and a resistor 24 in series, connected across coil 10a.

Electromagnet 10 has an E-core 10b which lies in a plane parallel toaxle 9 and has three pole faces confronting the armature 4, the centerleg of the core being surrounded by the coil 1011. Core 10b is composedof a stack of laminations, each parallel to the plane of E", whichpreferably consist of ferrosilicon. The core and its coil areadvantageously enclosed, at least in part, by a shield of soft iron orthe like designed to suppress stray flux.

The short lever arms of the low-inertia rocker 3 terminate, beyond thearmature 4, in free extremities 5 which are guided in slots 12 of baseplate 11a and form abutments arresting the forward swing of the rocker,upon energization of coil 10a, in a position in which the armature 4 isspaced from the confronting pole faces of core 10b whereas striker l isstill separated from the working surface of tape 15. The kinetic energydissipated upon contact of abutments 5 with the ends of slots 12 issmall, however, owing to the reduced mass of driving rocker 3, theworking rocker 2 thereupon continuing its swing against the force ofrestoring spring 8 to translate its own kinetic energy into theformation of an imprint on tape 15. The coaxial mounting of rockers 2and 3 eliminates any relative motion therebetween as long as they are incontact. Upon recall of the rocker 2 by the spring 8, this rockerreengages the boss 6 of rocker 3 which at that instant is still biasedforwardly, albeit at reduced force, by the residual magnetic field ofcore 1011. This residual field is maintained for a certain period afterthe disappearance of the short actuating pulse from generator 19 by theflow of inductive current through diode 23 and resistance 24, the lengthof that period being determined by the time constant of the circuitconstituted by resistance 24 and the inductance of coil 10a. Owing tothe damping effect of this residual field, vibrations of the movableassembly are minimized and the striker l is retracted with only slightimpact preparatorily to its next advance.

The command pulses on line 20 may be generated by a teleprinter or anyother conventional system designed to synchronize the occurrence ofthese pulses with the rotation of font wheel 17 in such a way that theadvance of hammerhead 11 coincides with the arrival of a desired typeface opposite tape 15. The advance of the tape by the rollers 16 is alsocorrelated with the printing operation in a manner known per se.

If the tape 15 consists of conventional self-contained paper in which acolorant is released by the pressure of a type face, the ribbon 18 willof course be omitted.

It will also be understood that a type carrier may be disposed (e.g., asshown in US. Pat. No. 3,442,365) between the striker 1 and the recordingmedium 15, the working surface being then the back of the type carrierwhich is displaced together with the medium against a stationary anvilunder the impact of the hammerhead.

I claim:

1. A print hammer comprising a support, a first rocker pivotally mountedon said support, a second rocker pivotally mounted on said support on acommon pivotal axle with said first rocker for swinging entrainmentthereby, a striker on said second rocker confronting a working surface,resilient means engaging said second rocker for holding same in contactwith said first rocker at a location remote from said axle while urgingsaid striker away from said working surface, electromagnetic actuatingmeans on said support, an armature on said first rocker confronting saidactuating means for displacement thereby to swing said first rocker in adirection driving said striker toward said printing surface against theforce of said resilient means, and abutment means for arresting theswing of said first rocker before said striker contacts said workingsurface.

2. A pring hammer as defined'in claim 1 wherein said first rockercomprises a pair of generally parallel levers fulcrumed on said axle,said armature spanning said levers.

3. A pring hammer as defined in claim 2 wherein each of said levers hasa short arm secured to said armature and a long arm with a free endbearing upon said second rocker.

4. A print hammer as defined in claim 3 wherein said first rocker is ofreduced mass compared with said second rocker.

5; A print hammer as defined in claim 4 wherein said first rockerconsists of lightweight material and said long arms have a widthdecreasing with increasing distance from said axle.

6. A print hammer as defined in claim 3 wherein said first rockerfurther comprises a bridge piece interconnecting the free ends of thelong arms of said levers, said bridge piece contacting said secondrocker at a location in line with said striker.

7. A print hammer as defined in claim 6, further comprising adjustablebackstop means on said support bearing upon said bridge piece forlimiting the reverse swing of said first rocker in response to saidresilient means.

8. A print hammer as defined in claim 3 wherein said actuating meanscomprises a coil with an E-core having three pole faces confronting saidarmature, said core lying in a plane parallel to said axle.

9. A print hammer as defined in claim 8 wherein said core consists offerrosilicon laminations parallel to said plane, said actuating meansfurther including permeable shield means for said core.

l0.A print hammer as defined in claim 3 wherein the short arms of saidlevers have free extremities extending beyond said armature and formingpart of said abutment means, said support comprising a base carryingsaid actuating means, said base being provided with guide slots for saidshort arms, the ends of said guide slots constituting stops for saidextremities.

11. A print hammer as defined in claim 1 wherein said actuating meanscomprises a coil and a damping circuit including a diode and aresistance connected across said coil.

1. A print hammer comprising a support, a first rocker pivotally mountedon said support, a second rocker pivotally mounted on said support on acommon pivotal axle with said first rocker for swinging entrainmentthereby, a striker on said second rocker confronting a working surface,resilient means engaging said second rocker for holding same in contactwith said first rocker at a location remote from said axle while urgingsaid striker away from said working surface, electromagnetic actuatingmeans on said support, an armature on said first rocker confronting saidactuating means for displacement thereby to swing said first rocker in adirection driving said striker toward said printing surface against theforce of said resilient means, and abutment means for arresting theswing of said first rocker before said striker contacts said workingsurface.
 2. A pring hammer as defined in claim 1 wherein said firstrocker comprises a pair of generally parallel levers fulcrumed on saidaxle, said armature spanning said levers.
 3. A pring hammer as definedin claim 2 wherein each of said levers has a short arm secured to saidarmature and a long arm with a free end bearing upon said second rocker.4. A print hammer as defined in claim 3 wherein said first rocker is ofreduced mass compared with said second rocker.
 5. A print hammer asdefined in claim 4 wherein said first rocker consists of lightweightmaterial and said long arms have a width decreasing with increasiNgdistance from said axle.
 6. A print hammer as defined in claim 3 whereinsaid first rocker further comprises a bridge piece interconnecting thefree ends of the long arms of said levers, said bridge piece contactingsaid second rocker at a location in line with said striker.
 7. A printhammer as defined in claim 6, further comprising adjustable backstopmeans on said support bearing upon said bridge piece for limiting thereverse swing of said first rocker in response to said resilient means.8. A print hammer as defined in claim 3 wherein said actuating meanscomprises a coil with an E-core having three pole faces confronting saidarmature, said core lying in a plane parallel to said axle.
 9. A printhammer as defined in claim 8 wherein said core consists of ferrosiliconlaminations parallel to said plane, said actuating means furtherincluding permeable shield means for said core.
 10. A print hammer asdefined in claim 3 wherein the short arms of said levers have freeextremities extending beyond said armature and forming part of saidabutment means, said support comprising a base carrying said actuatingmeans, said base being provided with guide slots for said short arms,the ends of said guide slots constituting stops for said extremities.11. A print hammer as defined in claim 1 wherein said actuating meanscomprises a coil and a damping circuit including a diode and aresistance connected across said coil.